Barbecuing meat, poultry or fish on an open fire can present the chef with many cooking variables in order to determine when the food is done. The heat may not be uniform, the thickness of the meat can be variable, and the standard doneness measurement such as “rare”, “medium” or “well done” can be quite subjective. Also, the relative thickness of the item being cooked can influence the amount of time necessary for proper preparation. For instance, cooking time might vary dramatically for a thin hamburger versus a thick steak. Similar variables occur with ovens and stoves due to temperature fluctuations of the heat source.
When meat, poultry, fish, etc. is heated for cooking (e.g., placed on a barbeque fire or in a hot oven, etc.) the surface of the food closest to the heat source will increase in temperature and a temperature gradient will occur across the thickness of the food with time as heat diffusion occurs. As such, the food will typically have a temperature gradient across the thickness of the food wherein, for example, portions of the food closest to the heat source will be hottest and portions of the food farthest from the heat source will be coolest. Accordingly, measuring the temperature at a single point within the food in order to determine the doneness of the food may not provide an accurate result.
One way to check the doneness of meat is to make a cut in the meat to visually observe the interior doneness during the cooking process. This method, however, is quite subjective and may allow internal juices to be lost thereby drying out the food. Another solution has been the use of irreversible thermochromic materials which, when placed in contact with the food, will show if the food has exceeded some critical temperature related to the doneness and/or safety of the food for eating (e.g., above some critical temperature that can kill bacteria). For example, a product called “T. Stick”, which is disclosed in U.S. Pat. No. 5,622,137 and sold by M. E. Heuck Co., uses an irreversible thermochromic material to show if meat, poultry, or pork has exceeded a given temperature. Another example of a product using irreversible indicators was patented by Hans O. Ribi. The Ribi device uses irreversible indicators that are coated onto a plastic probe as set forth in U.S. Pat. Nos. 5,685,641 and 5,918,981. Other Ribi devices include indicators that are small discreet reversible thermochromics dipped on a metal cylindrical carrier. Such devices, however, only measure temperature at a discreet point within the food.
Another product designed to aid in cooking is the “Tempfork”, developed by Mr. Richard Murtagh. The Tempfork uses a thermocouple or similar sensor disposed in the tines of a fork to probe the food and sense the temperature. This expensive battery-operated device is reusable, but only gives a temperature measurement at the localized point of insertion. Since the temperature measurement is localized, it can be inaccurate particularly when cooking food on an open fire (e.g., a grill) which typically has hot spots. In addition, the device creates a hole in the meat that, upon withdrawal of the device, generally remains open and allows juices to escape the meat.
All these products have a common design fault—they indicate the temperature or peak temperature at a particular location within the food even though the food may have a wide range of temperatures at various other locations. As mentioned, measuring the temperature at a single point within the food in order to determine the doneness of the food may not provide an accurate result.